Do Rice Hulls Prevent Weeds in Woody Ornamental Container Production in a Central Florida Growing Environment?

 

While making my rounds at various nurseries around the county I am finding more and more managers are utilizing parboiled rice hulls as a source of mulch for early weed control in container woody ornamental plantings.  The question is, "Do rice hulls prove to be both an economical and effective solution for weed control?"  When asking this question, I have a lot of anecdotal evidence of weed suppression during the early growth stage of container plant production, but I have very few facts to back up whether there is an economic benefit when comparing the cost of materials, labor costs and the difference between traditional weeding and a preemergent herbicide.

There is good evidence that rice hulls can reduce bittercress and liverwort when applied at depths of ½” to one inch thick on the surface of container soil (Atland, 2019).  Mulches play a crucial role in inhibiting weed growth by creating an unfavorable environment for seed germination. By covering the substrate surface, mulches restrict the access of small weed seeds to essential resources, such as stored energy and nutrients. However, most mulches eventually decompose and become conducive to weed germination, limiting their long-term effectiveness. 

Effective mulches for container crops should possess specific characteristics, including low nutrient content, quick drying properties, and resistance to decomposition. Rice hulls exhibit these desirable qualities, making them a potentially good choice for preventing the establishment of some weeds.

I have seen sawdust or shredded wood being used at nurseries but when I tested the cost and effectiveness in an experiment, there were no economical and no practical benefits compared to hand-weeding and preemergent herbicides. 

Dr. Chris Marble (UF Weed Scientist) and I did a mulch study and published the results. We found that large pine bark nuggets did well restricting weeds but when compared to thin plastic (the kind used for strawberry or vegetable fields); plastic mulch wins hands down (Marble et al, 2019). 

In another study of plastic mulch for weed control, I demonstrated that plastic mulch almost eliminated weeds, reduced water loss, reduced the need for irrigation, and reduced the leaching of fertilizer (Steed et al, 2018). I did find that plants grew slower in plastic mulch, but I speculate that it was due to the lack of leaching irrigation and a dramatic increase in EC and decrease in pH over the growth time
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Soon we will be experimenting with rice hulls and let you know whether it is a good idea to use them as a weed control method or not. 

References:

Atland, James.  2019.  USDA tests PBH rice hulls for weed control in container crops.  Nursery Management Magazine.

Marble, S. C., Steed, S. T., Saha, D., & Khamare, Y. 2019. On-farm Evaluations of Wood-derived, Waste Paper, and Plastic Mulch Materials for Weed Control in Florida Container Nurseries, HortTechnology hortte, 29(6), 866-873.

Steed, S.T., Bechtloff, A., Koeser, A. & Yeager, T. 2018. Response of Japanese privet to plastic mulch applied over nonspaced containers HortTechnology 28 58-65